The present disclosure is directed to a permanent magnet alternator, and more particularly directed to a shunt regulated permanent magnet alternator including margin detection.
Permanent Magnet Alternators (PMAs) are currently used as alternating current (AC) power sources for many electrical applications. A rotating shaft within the PMA causes the PMA to generate electrical power according to known power generation techniques. The rotating shaft can be tied to any source of mechanical rotation to provide the necessary rotational forces. The PMA is configured such that power from the PMA is regulated to provide a load with a direct current (DC) voltage source. In such a configuration, a shunt regulator is typically connected to the PMA, thereby allowing for excessive current, not used by the attached loads, to be shunted back to the PMA or to ground.
In order to control the shunt regulator, a pulse width modulation (PWM) controller provides a PWM control signal that cycles the shunt regulator on and off. When the shunt regulator is on, the current bypasses the load and is directly shunted to ground. Thus, the shunt regulator can be rapidly cycled on and off with the percentage of off time in each cycle determining the percentage of the available current seen by the load. Introduction of a new load onto the shunt regulated PMA necessarily causes an increase in the amount of current required by the loads. When the current required by all of the loads exceeds the available current of the shunt regulated PMA voltage source, the voltage across the shunt regulator decreases. When the voltage across the shunt regulator decreases beyond a certain threshold, the control system can reset, resulting in undesirable control behaviors.